The present invention is in the field of retardation layers for liquid crystalline displays comprising a twisted nematic liquid crystalline polymer film, more particularly in the field of retardation layers based on super-twisted nematic (STN) liquid crystalline layers. Such retardation layers are described in U.S. Pat. No. 5,382,648 and in European Patent Publication No. 380,338. For a further explanation of such retardation layers, reference may be had to these patent documents.
In theory, STN retardation layers can fully compensate the optical effects that occur in STN display cells. For this reason, STN retardation layers are regarded to be superior compared to uniaxially stretched polymer films. The required thickness of liquid crystalline polymer (LCP) STN retardation layers depends upon the birefringence of the LCP and is approximately 5-9 micrometers. Due to the low thickness of the LCP layer, in general, a suitable substrate (carrier) is used. Up until now, thick glass substrates (0.7 mm) have been used for low molecular twisted nematic materials. When used as such retardation layers, these thick substrates have several drawbacks. For example, these substrates are heavy and their use results in thick retardation layers.